When people asked how Buffett made money in investing, his usual response is "start with the A's" (referring to the Value Line manual). I have found that an unsatisfactory answer, though, because unless you have some idea of what you're looking for, "starting with the A's doesn't mean much."
A better example of Buffett's obsessiveness is that he used to pick up discarded race track tickets. The overwhelming majority were no good, of course, but you might find one in a thousand where a winning ticket had been absent-mindedly discarded and you could cash in on the bet.
But, well, the fund management industry do work hard, yet have little to show for it. An old investment classic (can't remember which) put it this way: a guy new an analyst that could tell you everything you wanted to know about every railway company, except which ones to invest in.
I think many good investments rely on just a few simple arguments. For example, back in 2021 I learned that the price of Shell shares were at their lowest point for a decade or so, oil was at a low, and the US strategic oil reserves were at their lowest level since the 80's. I figured, Jeez, how much lower can then stuff go? So I bought shares. They've nearly doubled. There's no guarantees with this stuff, of course, I've made plenty of mistakes. It also requires the availability of opportunities, naturally. Sometimes my primitive monkey brain can spot them. No guarantees, there never are, but sometimes you can spot opportunities where the odds are stacked in your favour, and those are the ones you want to dabble in.